1. Field of the Invention
The present invention relates to an optical disk apparatus and a method for controlling the same. The present invention is applicable to an optical disk apparatus, including a DVD+RW (digital video disk+read/write [with a recording capacity of 4.7 gigabytes]), DVD+R, and DVD-R/RW. The present invention allows for OPC (optimum power calibration) using the amount of jitter as an evaluation reference and using a small area compared to the related art, by switching an operational reference between a writing clock signal and a playback signal to generate a playback clock signal, and by switching the operation when test-writing data is played back.
2. Description of the Related Art
Conventionally, in an optical disk apparatus, OPC is used to set an optimum amount of light for writing, to cope with variations in the characteristics of the information-recording surface of optical disks.
That is, when an optical disk is loaded into an optical disk apparatus and then a command for writing is input, for example, an OPC area provided at the innermost circumference thereof is used to record test-writing data by changing the amount of light sequentially in a step-by-step manner, thereby executing so-called “test writing”. The optical disk apparatus is also configured such that it plays back the test-writing data recorded in this manner and uses the playback results based on a predetermined evaluation reference to determine an optimum amount of light.
In the case of, for example, a DVD+RW having a recording capacity of 3.0 gigabytes, as shown in part (A) of FIG. 9, data areas D, each occupying one block (32 kilobytes), extend with linking areas, each occupying one sector (2 kilobytes), interposed therebetween, so that data is recorded block by block. Thus, when test writing is performed while the amount of light varies over eight levels, the optical disk apparatus uses eight linking areas and eight blocks for the test writing. In this case, one block corresponds to a length of about one full revolution of the innermost circumference of the optical disk.
As an evaluation reference for such an optimum amount of light, the amount of jitter is determined from the playback result of the test-writing data and is used to determine the optimum amount of light. Thus, when test-writing data is recorded in the format as shown in part (A) of FIG. 9, the optical disk apparatus is configured such that a PLL circuit therein performs synchronization in a linking area and then the amount of jitter is measured from the test-writing data recorded in a data area with reference to a playback clock signal generated by the PLL circuit.
Referring to part (B) of FIG. 9, a DVD+RW having a recording capacity of 4.7 gigabytes has a format that does not include linking areas L. With such a DVD+RW, when conventional OPC is performed, successive blocks are sequentially allotted as areas for the synchronization of a PLL circuit and areas for recording test-writing data, thus posing a problem in that a large area is necessary for the OPC.
In contrast, in the case of an optical disk such as a DVD-R or DVD+R having an information-recording surface that is formed of organic dye, when a large area thereof is used for OPC, the information-recording surface cannot be effectively used due to the difficulty of re-writing. Thus, for such an optical disk on which it is difficult to re-write data, OPC needs to be performed with the smallest possible area and for the greatest possible number of times.